Insect-inspired mini-robots could be the smallest, lightest and fastest ever developed

Two insect-like robots, a mini-bug and a water walker, developed at Washington State University, are the smallest, lightest and fastest fully functional micro-robots ever created.

Such miniature robots could one day be used for work in areas such as artificial pollination, search and rescue, environmental monitoring, microfabrication or robot-assisted surgery. Reporting their work in the proceedings of the IEEE Robotics and Automation Society International Conference on Intelligent Robots and Systems, the mini-insect weighs eight milligrams while the water walker weighs 55 milligrams. Both can move at around six millimeters per second.

“It’s fast compared to other microrobots at this scale, although it still lags behind their biological parents,” said Conor Trygstad, a Ph.D. student in the School of Mechanical and Materials Engineering and lead author of the work. An ant typically weighs up to five milligrams and can move at nearly a meter per second.

The key to small robots is their tiny actuators that make them move. Trygstad used a new manufacturing technique to miniaturize the actuator to less than a milligram, the smallest ever made.

“The actuators are the smallest and fastest ever developed for microrobotics,” said Néstor O. Pérez-Arancibia, Flaherty associate professor of engineering in WSU’s School of Mechanical and Materials Engineering, who led the project.

The actuator uses a material called shape memory alloy, which is capable of changing shape when heated. It is called “shape memory” because it remembers and then returns to its original shape. Unlike a typical motor that would move a robot, these alloys have no moving parts or rotating components.

“They are very strong mechanically,” Trygstad said. “The development of this very lightweight actuator opens new areas in microrobotics.”

Shape memory alloys are generally not used for large-scale robotic movements because they are too slow. In the case of WSU robots, however, the actuators are made of two tiny shape-memory alloy wires with a diameter of 1/1000 of an inch. With a small amount of current, the wires can be heated and cooled easily, allowing the robots to flap their fins or move their feet up to 40 times per second. In preliminary tests, the actuator was also capable of lifting more than 150 times its own weight.

Compared to other technologies used to make robots move, SMA technology also requires only a very small amount of electricity or heat to make them move.

“The SMA system requires much less sophisticated systems to power it,” Trygstad said.

Trygstad, an avid fly fisherman, has long observed water striders and would like to study their movements further. While the WSU water robot performs a flat flapping motion to move, the natural insect performs a more efficient rowing motion with its legs, which is one of the reasons why the real thing can move around a lot faster.

The researchers would like to copy another insect and develop a water-walking robot capable of moving both above the surface of the water and just below it. They are also working on using tiny batteries or catalytic combustion to make their robots fully autonomous and without power supply.